Obesity is now one of the most serious public health problems facing American Indian children. Intervention studies, designed with the full participation of American Indian communities, are urgently needed to develop and test effective strategies for obesity prevention and control. The goal of the Walking to Health for American Indian Children pilot program is to assess the feasibility of a school-based environmental change intervention for promoting increased physical activity among American Indian children to reduce their risk of obesity. The school-based intervention consists of policy change to incorporate a daily one-mile walk for third and fourth grade students into the school day. The hypothesis is that it is feasible to integrate into the school day a Walking to Health program designed to reduce BMI and body fatness, increase physical activity, and increase preferences and self efficacy for walking and physical activity among participating students. The feasibility and initial impact of the program will be assessed through a pilot project in three elementary schools on two Indian reservations in northern Minnesota. The primary endpoint will be the extent and fidelity of program implementation. The secondary endpoints will be those that will become primary in a subsequent R01 submission for a full-scale study: (1) change in body mass index (BMI); (2) change in body composition; (3) change in average daily physical activity; and (4) change in attitudes and preferences for physical activity. The major aim of the feasibility trial is to prepare the programs (school environmental, outdoor walking, and family involvement), methods of evaluation (process and outcome) and setting (research design, school participation and family involvement) for a future full-scale research study.